1. Field of the Invention
The present invention relates to an operator control device for an infinitely variable transmission and in particular to a control device having a control lever that is movable between a minimum speed position and maximum speed positions and which has an intermediate set point position for which the operator can adjust a speed to be commanded when the lever is in the set point position.
2. Description of the Related Art
An infinitely variable transmission (IVT) has potential to provide a large range of speeds to a self-propelled work machine such as a construction machine, tractor, agricultural combine, cotton picker, forage harvester, etc. One benefit of an IVT is that it gives the operator the ability to select the speed that best matches the present task. The control device for the IVT needs to provide the operator with a means to adjust this speed. Currently available IVT control devices provide the operator with the ability to choose the desired speed. The means to choose the desired speed have been accomplished by various executions of two basic concepts. One concept provides a lever or similar device that is moved through a pattern to a position that corresponds to the desired speed. If a lever with good speed resolution is provided, i.e. the ability to make fine adjustments of the speed, the amount of lever travel will exceed the range of convenient reach for the operator. Likewise, a lever that is compact and convenient to reach does not provide sufficient speed resolution.
The other control concept provides a lever or similar device that only selects a travel direction based on the lever position, and by an alternate motion, incrementally increases or decreases the speed. For example, a lever that moves fore and aft to select the desired travel direction may also pivot left and right to increase and decrease speed respectively. The lever position only indicates travel direction but not the actual speed. The advantage of this concept is that the lever takes less space on the control console since it does not require a position for each speed. The lever is easy to reach for all speeds. A disadvantage of this concept is that the operator must hold the control lever to the left or right to increase or decrease the speed the entire time the vehicle speed is changing. To command a large speed change, the operator needs to hold the control lever in the proper position for the long time period required to accomplish the speed change. Some implementations of this control concept provide a means for the vehicle to remember a specific speed and easily return to it. This may be accomplished by a push button which, when depressed, remembers the current speed. This speed can be automatically returned to by moving the control lever to a specific position. The incrementing control must be used to attain speeds other than the remembered speed. This control does not provide a simple method to preset a vehicle speed prior to vehicle movement.